There are various medical cables such as probe cable, catheter cable and endoscope cable, etc., which use a coaxial cable as a signal line. Coaxial cables provided with a foam insulation layer formed around a central conductor by foam extrusion coating are conventionally known as coaxial cables to be used inside such medical cables (see, e.g., PTLs 1 and 2). It is possible to reduce capacitance of the insulation layer by air bubbles formed by foaming.
As the size of medical devices is reduced, medical cables are required to have a smaller diameter and diameters of coaxial cables accordingly tend to be reduced.
Meanwhile, PTL 3 discloses a coaxial cable which is not for medical use. This coaxial cable is formed by enclosing a wire-shaped inner conductor in an insulating member and further enclosing the insulating member in an outer conductor, and the insulating member is composed of insulating cords twisted around the inner conductor.